Generally, to drive a main drive motor provided in an electric vehicle, when the main drive motor is an induction motor, there is required a vehicle control device including a so-called variable voltage variable frequency (VVVF) inverter that supplies variable voltage variable frequency electric power to the induction motor, a converter used when wiring is an alternating current, and related devices or the like. The vehicle control device is installed using a limited space existing under a floor of a body of the electric vehicle, and many exothermic devices are used in the vehicle control device. Generally, the exothermic devices are forcibly cooled by a cooling unit having a radiator for cooling the exothermic devices, or by an air blower that sends cooling air to the radiator.
When vehicle control devices are classified based on the structure of their cooling units, the vehicle control devices can be roughly divided into a type of vehicle control device in which a cooling unit is detached in a rail surface direction (hereinafter, “bottom surface side of the electric vehicle”), and another type of vehicle control device in which a cooling unit is detached to a side surface direction of an electric vehicle. The cooling unit includes a snubber circuit component, which is a voltage-absorbing circuit component having a resistor, a semiconductor device such as an IGBT, a cooler that cools the lost heat generated by switching of the semiconductor device and the heat generated from the snubber circuit component, an electric wire and a conductor bar that electrically connect a capacitor for smoothing an output of the converter.
When the semiconductor device is operating, if a device applied voltage including a ripple voltage exceeds a device-maximum service voltage, the semiconductor device is broken in some cases. Therefore, to suppress the device applied voltage within a device-maximum service voltage, it is necessary to suppress an impedance value of an inductance between the semiconductor device and a capacitor within a specification value. In this inductance, an inductance of electric parts themselves such as the semiconductor device and the capacitor, and a wiring inductance caused by an electric wire and a conductor bar that electrically connects these parts with each other are included. Particularly, it has been known that when a distance between these parts is shortened, an impedance value of the wiring inductance can be reduced.
For example, a conventional vehicle control device described in Patent Document 1 mentioned below includes a cooling unit having a heat absorber that absorbs the heat of a semiconductor device, a voltage-absorbing circuit component, and a control circuit component, and also having a radiator that radiates the absorbed heat, as well as an air blower that sends cooling air to the radiator. The vehicle control device is accommodated in a casing-like control box (hereinafter, “vehicle control device casing”), and installed below a floor of an electric vehicle.
Patent Document 1: Japanese Patent Application Laid-open No. H07-251737